The frequent evaluation of bacteriological procedures, media, and biochemical reagents is mandatory in diagnostic microbiology laboratories to insure the correct identification of pathogenic microorganisms in clinical specimens. The accurate determination of antibiotic susceptibility also is highly dependent upon the routine standardization of media, antibiotic-impregnated discs, and procedures.
To assure the necessary high standards of media reliability and reproducibility in such laboratories, a supply of bacterial cultures which provides appropriate reactions is required. Such laboratories, therefore are confronted with the task of maintaining bacterial control cultures for quality control purposes. Currently, transfer on solid media and lyophilization are common practices used to maintain such control cultures. The disadvantages of such practices include the possible mutation and/or contamination of cultures, potential aerosolization of viable organisms from lyophilized cultures the need for expensive equipment, and the need for technical personnel. See, e.g., G. W. Douglas et al., Appl. Microbiol., 25, 230 (1973).
Recently, such problems have been lessened by the availability of commercial bacterial control cultures such as Bact-Chek.RTM. (Roche Diagnostics, Nutley, N.J.) and Bactrol Disks (Difco Laboratories, Detroit, Mich.). Unfortunately, such commercial bacterial control cultures in general do not include those bacterial species such as Haemophilus influenzae and Neisseria gonorrhoeae whose viability is difficult to maintain in vitro.
While such commercial bacterial control cultures also can be employed in industrial and research laboratories, such cultures do not appear to be readily adapted for use in industrial processes which utilize one or more biochemical conversions. This is especially true since many industrial processes more and more frequently are utilizing immobilized microbes. Thus, there is a growing need for immobilized process starter bacteria of constant and well-defined composition, whereby the biochemical conversions employing such immobilized bacteria can be optimized by the proper choice of bacteria. Immobilized bacteria having a known and constant composition also are required in the area of biochemical oxygen demand (BOD) determinations. The particular BOD reading which is obtained from such a determination is, to a large extent, dependent upon the nature of the bacteria employed. Since a company discharging waste into a stream can be fined on the basis of the BOD number, the number obtained becomes of critical importance. In addition, the generally unavailability of immobilized bacteria having a known and constant composition and adapted specifically for BOD determinations makes it extremely difficult to correlate BOD numbers obtained by various laboratories, even when efforts have been made to employ the same bacterial species.